(1) Field of the Invention
The present invention relates to a support device for a wafer shipping container for shipping silicon wafers and the like used in production of semiconductor products. More detailedly the present invention relates to a support device for a wafer shipping container suitable for keeping and transporting wafers which have been precision shaped and processed to an extra fine thickness with electronic circuitry interconnections patterned on the obverse side thereof and their reverse side ground by the backgrind process.
(2) Description of the Prior Art
A conventional wafer shipping container is comprised of a container body of a cylinder with a bottom, a cassette 6 set in this container body for holding multiple wafers in alignment with a pitch of a predetermined distance by holding slots 9, and a lid element being fitted on the open side of the container body with a gasket in between and a wafer presser optionally attached on the interior side of this lid element. Wafers W of a polished type with diameters of 6xe2x80x3 (about 150 mm) and 8xe2x80x3 (about 200 mm) are currently mass produced. The currently predominant wafers W are 625 xcexcm 725 xcexcm in thickness.
Wafer W having undergone various processes and shaping is patterned on its surface with electronic circuitry, then is transferred to the backgrind stage where its underside(rear side) is ground in conformity with the thickness specifications of the final product so as to form a backgrind wafer with its thickness precisely controlled to an extra thin level (50 xcexcm to 304 xcexcm). Such wafers W are very costly since electronic circuitry has been patterned on the obverse side but they are still easy to bend and break mechanically so that they should be handled very carefully (in respect to this, see FIG. 1).
Since the conventional wafer shipping container simply holds a multiple number of wafers W with holding slots 9 in cassette 6, wafers W are liable to rattle resulting from the combination of dimensional deviations of the wafer thickness and that of holding slots 9 of cassette 6 when backgrind-processed wafers W are stored in the container and shipped to another site for a next step such as a dicing process etc., and hence the wafers will relatively easily resonate due to vibrations during shipment. Further, since the conventional wafer shipping container has no member which fixes up the central part of wafers W which have been backgrind-processed, the amplitude of the vibrations becomes greater so that there is a high risk that wafers W may flex and interfere with each other or wafers W may vibrate beyond their strength limit, resulting in them being damaged or broken.
Still more, if even one of multiple large-diametric wafers W or one of multiple wafers with electronic circuitry formed thereon becomes broken during transportation, the broken pieces etc. can cause bad influence or secondary damage to the electronic circuitry of the other wafers W. In such an event, all the wafers W will become unusable for the most cases, resulting in a markedly high monetary loss.
In view of these problems, Japanese Patent Application Laid-Open Hei 9 No. 129719 and Japanese Patent Application Laid-Open Hei 9-246369 disclose a method whereby a cylinder portion of an approximate cylindrical shape is fixed upright in the container body of a wafer shipping container so as to keep a multiple number of wafers W horizontally in layers with cushioning elements interposed therebetween. However, this method needs dedicated equipment, hence posing a troublesome problem that the existing installation cannot be used any longer.
The present invention has been devised in view of the above problems, it is therefore an object of the present invention to provide a support device for a wafer shipping container, which can be used in existing equipment as is without the necessity of significant change, effectively remove the risks of the wafers relatively easily resonating due to vibrations and being damaged and broken and prevent the broken pieces of one wafer from adversely affecting the other wafers or causing secondary damage.
The present invention has been achieved in order to attain the above object, and the present invention is configured as follows:
In accordance with the first aspect of the present invention, a support device for a wafer shipping container, for constraining the flexure of a multiple number of backgrind-processed wafers when the wafers are stored in alignment in the wafer shipping container, is characterized in that stoppers for the support device are formed on the inner sides of the wafer shipping container, the support device is comprised of: a pair of opposing walls, which are positioned against the abutment side opposite to the open side of the wafer shipping container and fixed by the stoppers; a pair of connecting bars across the spacing between the paired opposing walls; a multiple number of partitioning supporters arranged with a predetermined pitch in the longitudinal direction of the connecting bars, and the wafers are inserted and held between adjoining partitioning supporters.
In accordance with the second aspect of the present invention, the support device for a wafer shipping container, having the above first feature is characterized in that the partitioning supporters are projected equal to or greater than one third of the wafer diameter to receive and hold the wafer between adjoining partitioning supporters.
In accordance with the third aspect of the present invention, the support device for a wafer shipping container, having the above first feature is characterized in that guide portions are formed at the distal part on the open side in the paired opposing walls of the support device.
In accordance with the fourth aspect of the present invention, the support device for a wafer shipping container, having the above first feature is characterized in that the multiple partitioning supporters of the support device are configured so that the spacing between adjoining partitioning supporters becomes gradually greater as it goes upwards, forming a wafer introductory guide, which serves as a guide when the wafer is fitted in.
In accordance with the fifth aspect of the present invention, the support device for a wafer shipping container, having the above first feature is characterized in that the multiple partitioning supporters are provided to span the spacing between, and perpendicularly to, the paired connecting bars at regular intervals.
In accordance with the sixth aspect of the present invention, the support device for a wafer shipping container, having the above first feature is characterized in that each of the partitioning supporters is formed of a plate-like element.
In accordance with the seventh aspect of the present invention, the support device for a wafer shipping container having the above first feature is characterized in that each of the partitioning supporters is formed of a pair of projecting bars inclined upwards with their top ends close to each other.
The wafer shipping container of the present invention may be of a top opening box type or a front opening box type. For keeping multiple wafers in alignment in this wafer shipping container, a multiple number of wafers may be put in alignment in a cassette then this cassette may be in turn placed into the container body. Alternatively, multiple holding slots may be integrally formed on both the interior side walls of the container body so that multiple wafers can be set in alignment using these holding slots without using any cassette. The material and diameter of the wafers to be handled, such as silicon wafers of, 3xe2x80x3, 6xe2x80x3, 8xe2x80x3and 12xe2x80x3, may be changed as appropriate. The wafers may be of any number but being at least two, 13, 25, 26 and so on. The abutment side of a wafer shipping container means the bottom (underside) if the wafer shipping container is a top open box type and the posterior side if the wafer shipping container is a front open box type.
Further, according to the present invention, by placing a multiple number of backgrind-processed wafers in alignment in the wafer shipping container, these wafers can be held between the partitioning supporters of the support device so that flexure of the wafers can be constrained by the partitioning supporters.